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2012 - 20133
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Subject: Silviculture and Agroforestry × End date: 2013 × Start date: 2010 × Type: Thesis ×
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    ThesisItemOpen Access
    Evaluation of seed source variation in Strychnos nux-vomica L. (Kanjiram) from different forest types of Kerala
    (Department of silviculture and agroforesty, College of forestry, Vellanikkara, 2012) Shine, G; KAU; Sudhakara, K
    A detailed investigation was conducted to evaluate the seed source variation in Strychnos nux-vomica L. (Kanjiram) from different forest types of Kerala through the estimation of variation in fruit traits, seed traits, germination attributes, seedling attributes, biomass estimation, alkaloid content and isozyme analysis. Identification of seed source variation of the species will be a valuable tool for its use in tree improvement programmes and by the cultivation of the tree on a commercial scale, pressure on natural stands can be reduced. The seed sources selected for the study were the dry deciduous forests of Chinnar Wildlife Sanctuary, moist deciduous forests of Pattikkad Forest Range and the riparian forests of Peechi Dam Site. The fruit parameters were tested with completely randomized design with unequal replications. The fruit traits viz. weight, volume and number of seeds per fruit, varied significantly (p<0.05) among the three seed sources and the highest values for these parameters were observed for the moist deciduous source and lowest were observed for the fruits of dry deciduous forests. The fruit weight and fruit volume were significantly correlated (p<0.01) to the number seeds per fruit. After the extraction, the seeds were categorized into four grades based on the seed size (average of the longest and its orthogonal diameter for each seed) viz., 27-30 mm, 24-27 mm, 21-24 mm and 18-21 mm. The subsequent tests on seed traits, germination attributes, seedling biomass and vigour index were done in factorial CRD and the seedling growth characteristics were tested in factorial RBD. The seeds from the dry deciduous source possessed the lowest length, width, size and weight. Seed thickness (5.3 mm) and seed density (0.53) were highest for the dry deciduous source and riparian source respectively. The regression equations were fitted for the density and weight by taking the seed size as the independent variable and were significant (p<0.05). The large sized seeds were significantly superior to the smaller ones with respect to the seed traits. The germination percentage and germination energy were similar for the dry deciduous (39%; 49%) and the riparian (38%; 44%) seed sources and were the lowest for the moist deciduous seed source (16%; 26%). Speed of germination (0.17), mean daily germination (0.54), peak value of germination (0.55) and germination value (0.34) for the dry deciduous source did not vary significantly (p<0.05) with that of riparian source; the moist deciduous source showed the lowest values. Germination attributes of larger seed grades were significantly superior compared to that of smaller seeds. From the final growth measurements it could be delineated that the seedling height (18.1 cm) was highest for the moist deciduous source and seedling collar diameter (3.6 mm) was highest for the dry deciduous source; but the riparian source produced the highest number of leaves per seedling. The seedlings from the larger seeds showed the greater growth. Seedling biomass production did not vary significantly among the seed sources and grades. Seedling vigour indices for the dry deciduous and riparian sources were significantly (p<0.05) higher to that of moist deciduous source. Highest strychnine content (3683 ppm) was obtained from the moist deciduous source and the highest brucine content (1692 ppm) was obtained from dry deciduous source. The riparian source possessed significantly (p<0.05) lowest alkaloid content. The presence of esterase was conformed in the seedling leaf extracts of all the three seed sources without any variations. Studies on different characteristics on the fruits, seeds and seedlings of Strychnos nux-vomica, revealed that the best performed seed source was the dry deciduous forest source and the poorest was the moist deciduous forest source. The results of this study will be useful in Strychnos nux-vomica for increasing the germination, seedling growth and to get higher quantities of alkaloids through breeding programmes.
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    ThesisItemOpen Access
    Biomass production and nutrient dynamics in a multipurpose tree based black pepper production system
    (Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2013) Aneesh, S; KAU; Kunhamu, T K
    A field study was undertaken on a 22-year-old black pepper production system at Livestock Research Station, Thiruvizhamkunnu, Kerala during 2009-10 to evaluate the growth, biomass production, Carbon sequestration and nutrient dynamics in six multipurpose trees used as pepper standards viz. Acacia auriculiformis, Artocarpus heterophyllus, Grevillea robusta, Macaranga peltata, Ailanthus triphysa and Casuarina equisetifolia. Diameter at breast height (DBH), total height and bole height varied significantly between the six species. Maximum DBH was registered by Grevillea robusta (23.06 cm) which was closely followed by Artocarpus heterophyllus (22.12 cm). Mean tree total volume and bole volume production also varied, maximum mean tree bole volume was recorded by Grevillea robusta (0.360 m3) followed by Artocarpus heterophyllus (0.280 m3) and Acacia auriculiformis (0.260 m3). The aboveground biomass was estimated from destructively sampled 12 trees of each species and the belowground biomass was estimated following root excavation of three average sized trees of each species. Species-wise variation in terms of total biomass, aboveground biomass and belowground biomass was observed. Among the black pepper support trees Grevillea robusta recorded highest total biomass production (366 Mg ha -1) followed by Acacia auriculiformis (331 Mg ha -1) and the lowest was recorded in Ailanthus triphysa which is 155 Mg ha-1. The above ground biomass ranged from 264 Mg ha-1 in the case of Grevillea robusta to lowest of 122 Mg ha-1 in the case of Macaranga peltata. Stem wood accounted for maximum contribution to the total biomass in all the species. Maximum root biomass was recorded in the case of Grevillea robusta (63 Mg ha-1) closely followed by Acacia auriculiformis (62 Mg ha-1) and the lowest in the case of Ailanthus triphysa (24 Mg ha-1). Percentage contribution of root biomass to the total biomass varied from 11 to 24 depending on the species. Among different pepper support tree system, the Grevillea robusta based pepper production system recorded highest biomass Carbon stock to the tune of 169.24 Mg C ha-1. However with regard to soil Carbon Acacia auriculiformis based pepper production system recorded highest value (71.39 Mg ha-1) followed by Macaranga peltata (68.64 Mg ha-1) based system while the treeless control plot recorded the lowest carbon stock (38.17 Mg ha-1). Study indicate the overall improvement in site productivity in multipurpose tree based production systems and careful selection of the tree species can bring substantial benefits both in economic and ecological terms to the farmer.
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    ThesisItemOpen Access
    Belowground architecture and carbon stocks of silver oak (Grevillea robusta A.Cunn) trees
    (Department of Silviculture and Agroforestry, College of forestry, 2013) Samritika; KAU; Kunhamu, T K
    Tree root biomass production and turnover play key role in improving soil productivity in land use systems involving woody perennials. Also, tree roots provide substantial contribution to the soil carbon pool which however varies with tree species and management regimes. A field study was conducted at Vellanikkara, Kerala, India in a 21-year-old Grevillea robusta stand (460 trees ha-1) to quantify the extent of belowground biomass production, root distribution pattern and carbon sequestration along with soil carbon stocks. A total of 18 trees were excavated using destructive sampling. The study also explored the distribution of C, N, P and K in the various root girth fractions (0-10 cm, 11-20 cm, 21-30 cm, 31-40 cm and tap root) and at various soil depths up to one meter. Mean tree root biomass production based on diameter class ranged from 12.94 to 59.81 kg tree-1 with a mean annual increment (MAI) varying from 0.62 to 2.85 kg tree-1 yr-1 while root biomass production at the stand level was 18.45 Mg ha-1 with a MAI of 0.88 Mg ha-1 yr-1. Based on the diameter class elemental carbon storage in the belowground root biomass of a mean tree varied from 5.58 to 23.58 kg tree-1. Grevillea robusta stand sequestered 8.04 Mg C ha-1 and 77.45 Mg C ha-1 in the root system and soil respectively. On the whole, the net belowground carbon sequestration (soil + roots) was 80.28 Mg C ha-1. Mean nutrients content (kg tree-1) in a mean tree roots were found to be 0.059 kg tree-1 N, 0.003 kg tree-1 P and 0.047 kg tree-1 K. While on the kg ha-1 basis N, P and K in a mean tree were found to be 25.89 kg ha-1, 1.70 kg ha-1 and 21.69 kg ha-1 respectively. Overall, the partitioning in the nutrient content among the root girth classes was found to be in order of tap root > 0-10 cm >11-20 cm > 21-30 cm > 31-40 cm. Logarithmic spiral trenching was used to study the root distribution pattern using 15 trees. The results revealed a decrease in rooting intensity with increasing lateral distance from tree base. With regards to lateral distance alone as a factor of determining the rooting intensity about 78 % roots were found to be within 1.55 m lateral distance. While using only depth as the sole criteria 74.51 % roots were found confined within top 30 cm depth. This clearly revealed the presence of majority of Grevillea robusta roots in the surface. Another study conducted using 32P study revealed that for 21-year-old Grevillea robusta trees, the active foraging zone lies within top 30 cm depth and 150 cm lateral distance. Overall uniformity in root distribution pattern obtained from excavation, logarithmic spiral trenching and 32P tracer study further demonstrate the surface feeder nature of Grevillea robusta roots. The higher root biomass and C sequestration in Grevillea robusta suggest its potential to enrich the soil nutrient status and there by offering better understorey productivity in polyculture systems involving silver oak. The root distribution trends though suggest silver oak to be a surface feeder, appropriate density management and planting geometry regulation makes it possible to try intercrops beyond a lateral distance of 2.0 m from the tree base.